Formation of phosphor regions for broad-area lighting systems

ABSTRACT

In accordance with certain embodiments, phosphor arrangements are formed via adhering phosphors to activated regions on a substrate and transferring them to a different substrate.

RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 61/567,302, filed Dec. 6, 2011, and U.S.Provisional Patent Application No. 61/589,908, filed Jan. 24, 2012, theentire disclosure of each of which is hereby incorporated herein byreference.

FIELD OF THE INVENTION

In various embodiments, the present invention generally relates toelectronic devices, and more specifically to array-based electronicdevices.

BACKGROUND

Light sources such as light-emitting diodes (LEDs) are an attractivealternative to incandescent and fluorescent light bulbs in illuminationdevices due to their higher efficiency, smaller form factor, longerlifetime, and enhanced mechanical robustness. However, the high cost ofLEDs and associated heat-sinking and thermal-management systems havelimited the widespread utilization of LEDs, particularly in broad-areageneral lighting applications.

The high cost of LED-based lighting systems has several contributors.LEDs are typically encased in a package, and multiple packaged LEDs areused in each lighting system to achieve the desired light intensity. Inorder to reduce costs, LED manufacturers have developed high-power LEDsthat emit relatively higher light intensities by operating at highercurrents. While reducing the package count, these LEDs requirehigher-cost packages to accommodate the higher current levels and tomanage the significantly higher resulting heat levels. The higher heatloads and currents, in turn, typically require more expensivethermal-management and heat-sinking systems which also add to the cost(as well as to the size) of the system. Higher operating temperaturesmay also lead to shorter lifetimes and reduced reliability. Finally, LEDefficacy typically decreases with increasing drive current, so operationof LEDs at higher currents generally results in a reduction in efficacywhen compared to lower-current operation.

A further problem associated with using fewer high-power LEDs inbroad-area Lighting—for example, to replace fluorescent lightingsystems—is that the light must be expanded from the relatively smallarea of the die (on the order of 1 mm²) to emit over a relatively largearea (on the order of 1 ft² or larger). Such expansion often results indecreased efficiency, reduced performance, and increased cost. Forexample, a light panel may be edge-lit and incorporate features thatredirect or scatter light. However, it is often difficult to achieveuniform light intensity over the entire emitting area of such panels,with the intensity generally being higher at the edge(s) near the lightsources. Also, the emission pattern from such devices is typicallyLambertian, resulting in poor utilization of light and relatively highglare.

An alternate approach to producing broad-area lighting is to use a largearray of small LEDs positioned over the desired emitting area. Such LEDsmay be unpackaged LEDs (i.e., LED dies) or packaged within, e.g., aleadframe and polymeric encapsulation. This tends to reduce the cost andefficiency losses associated with optics required to spread out lightfrom a small number of high-power LEDs. However, this approach typicallyinvolves forming an array of a very large number of light emitters overa relatively large area. In many such approaches the substrate uponwhich the light emitters are formed may be mated with other materials toaid in integration of phosphors, optics or for protection of thelight-emitter sheet.

Lighting systems have a wide range of specifications, for example forluminous efficacy, light output power, color temperature, colorrendering index (CRI) and the like. Many of these specifications arerelated to the LEDs, the light-conversion material (utilized to shiftthe wavelength of light from the LEDs to another wavelength, resultingin, e.g., white light), and the interaction between the two. Inparticular, various specifications in large measure determine theluminous efficacy, the color temperature, and the CRI. Uniformity ofthese characteristics is another key specification for lighting systemsand the uniformity of the luminous efficacy, color temperature, and CRIare typically directly dependent on the homogeneity of the LED andlight-conversion materials.

In array based lighting systems it can be difficult to achieveacceptable uniformity of the light-conversion material. Typically thephosphor powder is mixed in a binder, for example silicone, and this isapplied or dispensed to the LEDs. The phosphor powder may segregate inthe binder, resulting in a non-homogeneous distribution of phosphor inthe binder associated with each LED. A second complication is that thebinder may start to cure, even at room temperature, during theapplication process. Partial curing of the binder during the applicationprocess may result in non-uniform phosphor coverage.

These issues may apply to many types of phosphor-converted lightemitters, including single-LED packaged devices, multiple-LED packageddevices, arrays of LED and single or arrays of unpackaged LED (die) towhich phosphor is applied. In some systems it is desirable to integratethe LEDs and phosphor with one or more optical elements (e.g., a lens)to control the light-distribution pattern. Optical alignment of the LEDand phosphor with the optical element(s) is often important to achievethe desired light-distribution pattern and high optical efficiency.

In view of the foregoing, a need exists for the uniform and low-costapplication of phosphors to LEDs, and in particular either selectivelyor with full coverage over arrays of LEDs, as well as for economical,reliable LED-based lighting systems based thereon. A need also existsfor improvements in integration and alignment of optical elements withLEDs and phosphors.

SUMMARY

In accordance with certain embodiments, multiple phosphor arrangements(i.e., portions with or without a predefined shape) are formed inparallel via the activation (i.e., alteration to attract phosphorparticles) of particular regions on a first substrate, adherence of thephosphor (e.g., in powder form) to the activated regions, and transferof the phosphor regions to a second substrate. The first substrate maybe shaped in order to provide the adhered phosphors the predefinedshape, and the phosphors may be partially or substantially completelycured (i.e., heated to agglomerate together alone or within a bindermaterial) before or after transfer to the second substrate. The secondsubstrate may incorporate light-emitting elements (LEEs) thereon thatmay be at least partially covered or encased by the phosphorarrangements. In this manner, large arrays of LEEs may be integratedwith phosphors controllably, repeatably, and in parallel. The regions ofthe first substrate may be activated and deactivated via selectiveintroduction and removal of an electric charge, which may be introducedvia, e.g., application of electrical voltage and/or light. The formationof the phosphor arrangements may even be performed on large scales witha roll-to-roll process

Herein, two components such as light-emitting elements, opticalelements, phosphor portions, and/or other portions of lightsheets oroptical substrates (e.g., holes or wells (i.e., depressions or otherrecessed regions)) being “aligned” or “associated” with each other mayrefer to such components being mechanically and/or optically aligned. By“mechanically aligned” is meant coaxial or situated along a parallelaxis. By “optically aligned” is meant that at least some light (or otherelectromagnetic signal) emitted by or passing through one componentpasses through and/or is emitted by the other.

As utilized herein, an “optical substrate” is a material for receiving,manipulating, and/or transmitting light. An optical substrate mayinclude or consist essentially of, e.g., a transparent or translucentsheet or plate, a waveguide and/or one or more (even an array of)optical elements such as lenses. For example, optical elements mayinclude or consist essentially of refractive optics, reflective optics,Fresnel optics, total internal reflection optics, and the like. Theoptical substrate may include features or additional components ormaterials to scatter, reflect, or absorb light or a portion of light inthe optical substrate, and it may confine light by total internalreflection prior to its emission from the optical substrate. An opticalsubstrate comprising a plurality of optical elements is preferably aunitary substrate having the optical elements formed therein or thereon.

As utilized herein, the term “light-emitting element” (LEE) refers toany device that emits electromagnetic radiation within a wavelengthregime of interest, for example, a visible, infrared or ultravioletregime, when activated, by applying a potential difference across thedevice or passing a current through the device. Examples oflight-emitting elements include solid-state, organic, polymer,phosphor-coated or high-flux LEDs (bare-die or packaged), microLEDs,laser diodes or other similar devices as would be readily understood.The emitted radiation of a LEE may be visible, such as red, blue orgreen, or invisible, such as infrared or ultraviolet, and may have asingle wavelength or a spread of wavelengths. A LEE may feature aphosphorescent or fluorescent material for converting a portion of itsemissions from one set of wavelengths to another. A LEE may includemultiple constituent LEEs, each emitting at essentially the same ordifferent wavelength(s). In some embodiments, a LEE is an LED that mayfeature a reflector over all or a portion of its surface upon whichelectrical contacts are positioned. The reflector may also be formedover all or a portion of the contacts themselves. In some embodiments,the contacts are themselves reflective.

A LEE may be of any size. In some embodiments, a LEEs has one lateraldimension less than 500 μm. Exemplary sizes of a LEE may include about250 _(μ)m by about 600 μm, about 250 μm by about 400 μm, about 250 μm byabout 300 μm, or about 225 μm by about175 μm. In some embodiments, a LEEincludes or consists essentially of a small LED die, also referred to asa “microLED.” A microLED generally has one lateral dimension less thanabout 300 μm. In some embodiments, the LEE has one lateral dimensionless than about 200 μm or even less than about 100 μm. For example, amicroLED may have a size of about 225 μm by about 175 μm or about 150 μmby about 100 μm or about 150 μm by about 50 μm. In some embodiments, thesurface area of the top surface of a microLED is less than 50,000 μm² orless than 10,000 μm². However, the size and/or shape of the LEE is not alimitation of the present invention.

As used herein, “phosphor” refers to any material that shifts thewavelengths of light irradiating it and/or that is luminescent,fluorescent, and/or phosphorescent, and is utilized interchangeably withthe term “light-conversion material.” As used herein, a “phosphor” mayrefer to only the photoactive powder or particles or to the powder orparticles within a polymeric binder. The specific components and/orformulation of the phosphor and/or binder material are conventional andnot limitations of the present invention. The binder may also bereferred to as an encapsulant or a matrix material.

In an aspect, embodiments of the invention feature a method of formingan arrangement of phosphors. One or more regions of a first substrateare activated, whereby the one or more regions attract phosphor powder.Phosphor powder is introduced to the first substrate, the phosphorpowder adhering to the one or more activated regions of the firstsubstrate but not to other regions. The adhered phosphor powder istransferred to a second substrate different from the first substrate,thereby forming the arrangement of phosphors.

Embodiments of the invention may feature one or more of the following inany of a variety of combinations. The one or more regions of the firstsubstrate may each be a portion of a non-photoconductive surface. Theone or more regions of the first substrate may each be a portion of aphotoconductive surface. Activating the one or more regions may includeor consist essentially of (i) inducing an electrical charge on theentire photoconductive surface and (ii) illuminating portions of thephotoconductive surface other than the one or more regions to diminishthe charge on the illuminated portions. Activating the one or moreregions may include or consist essentially of inducing an electricalcharge thereon. The one or more regions of the first substrate may beconductive regions in or on the first substrate. An opposite electricalcharge (i.e., a charge having a polarity opposite that of the electricalcharge on the one or more regions) may be induced on the phosphor powderprior to adhering the phosphor powder to the one or more activatedregions. Transferring the adhered phosphor powder to the secondsubstrate may include or consist essentially of inducing an electricalcharge on the second substrate. Transferring the adhered phosphor powdermay include or consist essentially of at least partially removing theelectrical charge from the one or more regions of the first substrate.

One or more light-emitting elements may be associated (e.g., aligned)with each phosphor such that at least a portion of light emitted by eachlight-emitting element is converted to a different wavelength by theassociated phosphor. A transparent material may be disposed over atleast one of the phosphors before associating the one or morelight-emitting elements with each phosphor. Associating the one or morelight-emitting elements with each phosphor may include or consistessentially of bonding to the second substrate a third substrate havingthe one or more light-emitting elements thereon, whereby each phosphoris aligned with one or more light-emitting elements. The adheredphosphor powder may be transferred to indented regions in the secondsubstrate. Associating the one or more light-emitting elements with eachphosphor may include or consist essentially of disposing one or morelight-emitting elements in each indented region. The one or moreactivated regions of the first substrate may be indented, and theadhered phosphor powder may be transferred to one or more complementarystructures on the second substrate. Each of the complementary structuresmay include one or more light-emitting elements therein. The phosphorpowder may include or consist essentially of phosphor particles and abinder. The binder may be heated to fix the phosphor powder in placeafter transfer to the second substrate. The activating, introducing, andtransferring steps may each be performed as part of a roll-to-rollprocess.

In another aspect, embodiments of the invention feature a roll-to-rollapparatus for fabricating phosphor arrangements that includes orconsists essentially of a first roll for supplying a continuous lengthof a flexible substrate material, a second roll for accepting thecontinuous length of flexible substrate material from the first roll, adie-attach tool, a rotatable drum having a photoconductive surface, afirst dispenser for dispensing phosphor powder over the photoconductivesurface, and an illuminator. The die-attach tool attaches light-emittingelements to the flexible substrate material as the flexible substratematerial travels from the first roll to the second roll. The rotatabledrum is configured to dispose portions of phosphor over the flexiblesubstrate material as the flexible substrate material travels from thefirst roll to the second roll. The first dispenser is disposed over atleast a portion of the drum. The illuminator selectively illuminatesportions of the photoconductive surface as the drum rotates to renderthe illuminated portions attractive to the dispensed phosphor powder.The second roll accepts flexible substrate material havinglight-emitting elements each with a phosphor portion disposed thereover.The apparatus may include, disposed between the die-attach tool and thedrum, a second dispenser for dispensing a binder material over thelight-emitting elements after attachment thereof to the flexiblesubstrate material. The apparatus may include a scanning system forscanning light from the illuminator over the photoconductive surface.

In yet another aspect, embodiments of the invention feature aroll-to-roll apparatus for fabricating phosphor arrangements thatincludes or consists essentially of a first roll for supplying acontinuous length of a flexible substrate material, a second roll foraccepting the continuous length of flexible substrate material from thefirst roll, a third roll for supplying a continuous length of a secondsubstrate material, a die-attach tool, a rotatable drum having aphotoconductive surface, a first dispenser for dispensing phosphorpowder over the photoconductive surface, an illuminator, and anarrangement of rollers. The die-attach tool attaches light-emittingelements to the second substrate material after the second substratematerial is supplied by the third roll. The rotatable drum is configuredto dispose portions of phosphor over the flexible substrate material asthe flexible substrate material travels from the first roll to thesecond roll. The first dispenser is disposed over at least a portion ofthe drum. The illuminator selectively illuminates portions of thephotoconductive surface as the drum rotates to render the illuminatedportions attractive to the dispensed phosphor powder. The arrangement ofrollers is configured to bring the second substrate material and theflexible substrate material in proximity at a joining location after (i)light-emitting elements have been attached to the second substratematerial and (ii) phosphor portions have been disposed over the flexiblesubstrate material, thereby enabling transfer of the light-emittingelements to the phosphor portions over the flexible substrate material.The second roll accepts flexible substrate material havinglight-emitting elements each with a phosphor portion disposed thereover.The apparatus may include, disposed between the drum and the joininglocation, a second dispenser for dispensing a binder material over thephosphor portions after disposal thereof over the flexible substratematerial. The apparatus may include a scanning system for scanning lightfrom the illuminator over the photoconductive surface.

These and other objects, along with advantages and features of theinvention, will become more apparent through reference to the followingdescription, the accompanying drawings, and the claims. Furthermore, itis to be understood that the features of the various embodimentsdescribed herein are not mutually exclusive and can exist in variouscombinations and permutations. Reference throughout this specificationto “one example,” “an example,” “one embodiment,” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the example is included in at least one example ofthe present technology. Thus, the occurrences of the phrases “in oneexample,” “in an example,” “one embodiment,” or “an embodiment” invarious places throughout this specification are not necessarily allreferring to the same example. Furthermore, the particular features,structures, routines, steps, or characteristics may be combined in anysuitable manner in one or more examples of the technology. As usedherein, the term “substantially” means ±10%, and in some embodiments,±5%. The term “consists essentially of” means excluding other materialsthat contribute to function, unless otherwise defined herein.Nonetheless, such other materials may be present, collectively orindividually, in trace amounts.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawings, in which:

FIGS. 1 and 2 are flow charts depicting fabrication processes inaccordance with various embodiments of the present invention;

FIGS. 3, 4A, and 4B are cross-sectional schematics illustrating steps offabrication processes for phosphor arrangements in accordance withvarious embodiments of the present invention;

FIGS. 5 and 6 are cross-sectional schematics of substrates incorporatingregions that may be activated to attract phosphors in accordance withvarious embodiments of the present invention;

FIG. 7 is a plan view schematic of a substrate incorporating regionsthat may be activated to attract phosphors in accordance with variousembodiments of the present invention;

FIGS. 8A and 8B are cross-sectional schematics illustrating steps offabrication processes for phosphor arrangements in accordance withvarious embodiments of the present invention;

FIGS. 9-14 are cross-sectional schematics of substrates incorporatingphosphor arrangements as well as regions of transparent material and/orlight-emitting elements in accordance with various embodiments of thepresent invention;

FIGS. 15 and 16 are cross-sectional schematics illustrating steps offabrication of the structure of FIG. 14 in accordance with variousembodiments of the present invention;

FIG. 17 is a cross-sectional schematic of a substrate incorporatingphosphor arrangements as well as regions of transparent material andlight-emitting elements in accordance with various embodiments of thepresent invention;

FIG. 18 is a cross-sectional schematic of a fabrication step utilized toform the structure of FIG. 17 in accordance with various embodiments ofthe present invention;

FIGS. 19-21 are cross-sectional schematics of illustrating steps offabrication processes for phosphor arrangements in accordance withvarious embodiments of the present invention;

FIGS. 22-25 are cross-sectional schematics of illustrating steps offabrication processes for phosphor arrangements in accordance withvarious embodiments of the present invention;

FIGS. 26, 27A, 27B, 28, and 29 are cross-sectional schematics ofillustrating steps of fabrication processes for phosphor arrangements inaccordance with various embodiments of the present invention; and

FIGS. 30 and 31 are cross-sectional schematics of reel-to-reel systemsfor fabrication of phosphor arrangements and integration of phosphorarrangements with light-emitting elements in accordance with variousembodiments of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a flow chart depicting a process 100 in accordance with anembodiment of the present invention. Process 100 is shown as having fivesteps, but this is not a limitation of the present invention and inother embodiments the invention has more or fewer steps and/or the stepsmay be performed in a different order. Process 100 begins with step 210in which a first surface is provided. In step 220 a portion orsubstantially all of the first surface is activated, i.e., treated toattract a powder (e.g., a phosphor powder) to the activated areas; inother words, an activated area is one that attracts a phosphor powderand, when deactivated, does not exert this attraction. In step 230 oneor more powders are attached to the activated portions of the firstsurface. In step 240 a second surface is provided (the second surfacemay also be referred to as a target surface), and in step 250 one ormore portions or substantially all of the powder(s) are transferred tothe second surface.

As mentioned above, embodiments of the present invention may includeadditional steps. FIG. 2 is a flow chart depicting a process 200featuring three additional optional steps. In optional step 243 thefirst surface having the powder(s) attached thereto is brought intoproximity or contact with the second surface. In optional step 246 theactivation is reduced or removed after the surfaces are brought intoproximity or contact in order to reduce or eliminate the attractiveforce attaching the powder to the first surface. In optional step 260the first surface is removed from the second surface.

In various embodiments of the present invention, the first surfacereferred to in FIGS. 1 and 2 is an insulating surface into or onto whichconductive regions have been formed, as shown in FIG. 3. FIG. 3 depictsa structure 300 including or consisting essentially of an insulatingsubstrate 310 and conductive regions 320 in a surface thereof,corresponding to step 210 in FIG. 1. As per step 220 of FIG. 1, theconductive regions 320 are activated by, e.g., placing a charge, forexample a static electrical charge, on the conductive regions 320. Insome embodiments the charge is a positive charge while in otherembodiments the charge is a negative charge.

Insulating substrate 310 may include or consist essentially of, forexample, acrylic, polycarbonate, polyethylene naphthalate (PEN),polyethylene terephthalate (PET), polycarbonate, polyethersulfone,polyester, polyimide, polyethylene, glass, Teflon or the like. Eachconductive region 320 may include or consist essentially of a metal, forexample gold, silver, aluminum, or the like, carbon, a conductive oxide,or any other electrically conductive material, or any material capableof holding an electrical or static electrical charge. Conductive region320 may be formed over insulating substrate 310, for example usingphysical vapor deposition, chemical vapor deposition, sputtering, etc.or may be pre-formed and attached to insulating substrate 310 orpartially inserted into wells (or other depressions) in insulatingsubstrate 310. The material and method of formation of conductive region320 is not a limitation of the present invention. In some embodimentsconductive regions 320 are covered or partially covered by an insulatinglayer (not shown in FIG. 3). Substrate 310 may be non-photoconductive.

As described above in step 230, one or more powders are attached toregions 320 after regions 320 are activated. In some embodiments this isaccomplished by charging the powder(s) with the opposite charge of thatplaced on conductive regions 320 in step 220. The oppositely chargedpowders or particles will thus be attracted to charged conductiveregions 320 and adhere to them. FIGS. 4A and 4B depict one suchembodiment of the present invention. FIG. 4A depicts system 300 in whicha positive charge has been placed on the conductive regions 320. Then,system 300 is partially or completely immersed in a powder 410 having anegative charge. As shown in FIG. 4B, after removal of system 300 frompowder 410, portions 430 of powder 410 are attached to the conductiveregions 320. Powder 410 is shown in FIGS. 4A and 4B as contained in atray 420; however, this is not a limitation of the present invention andin other embodiments powder 410 is contained and/or applied to system300 in any of a variety of different ways. For example, in otherembodiments powder 410 is applied using a roller, by spraying, pouring,or shaking the powder on the surface of the insulating substrate 310into or onto which the conductive regions 320 have been formed. FIGS. 4Aand 4B depict conductive regions 320 having a positive charge and powder410 having a negative charge, but in other embodiments the polaritiesare reversed. In one embodiment powder 410 is a dry powder. In oneembodiment powder 410 is mixed in a solution, for example isopropylalcohol. In one embodiment the system shown in FIGS. 4A and 4B isconfigured for electrophoretic deposition.

Conductive regions 320 may be electrically coupled together or they maybe addressable. FIG. 5 shows one embodiment in which conductive regions320 are electrically coupled by conductive elements 510 that connectconductive regions 320 to an electrical trace 520 on the opposite sideof insulating substrate 310. FIG. 6 shows another embodiment in whichconductive regions 320 are electrically coupled by electrical traces 520that are at least partially covered by an insulating layer 610. WhileFIG. 5 shows only one electrical trace 520, this is not a limitation ofthe present invention and in other embodiments, multiple electricaltraces 520 are utilized.

FIG. 7 shows a plan view of the system 300 in accordance with variousembodiments of the present invention. In FIG. 7 the conductive regions320 are shown as having a square shape, but this is not a limitation ofthe present invention and in other embodiments conductive regions arecircular, hexagonal, rectangular, oval, or have any arbitrary shape.FIG. 7 shows conductive regions 320 arranged in a regular periodicsquare array, but this is not a limitation of the present invention andin other embodiments conductive regions 320 are arranged in otherpatterns, for example rectangular, triangular, hexagonal, or any otherarray, or are laid out in an arbitrary pattern.

FIGS. 8A and 8B illustrate an exemplary embodiment of step 250 from FIG.1 in which the powder portions 430 are transferred to a second or targetsubstrate 810. FIG. 8A depicts the optional step 243 from FIG. 2, inwhich the insulating substrate 310 with powder 430 over conductiveregions 320 is brought into contact with target substrate 810. FIG. 8Bshows the structure of FIG. 8A at a later stage of manufacture, i.e.,after step 250 of transferring powder 430 to target 810 and afteroptional step 260 of FIG. 2 in which insulating substrate 310 has beenremoved from target 810, forming a structure 800 that includes orconsists essentially of the target substrate 810 with the powderportions 430 thereon.

In some embodiments the optional step 246 from FIG. 2 is performed toremove the activation from (or “deactivate”) conductive regions 320before step 250 of transferring powder 320 to target 810. In someembodiments removing the activation includes or consists essentially ofreducing or eliminating the charge on conductive regions 320. In someembodiments removing the activation includes or consists essentially ofchanging the polarity of the charge on conductive regions 320. A chargewith a polarity opposite the polarity of the charge on conductiveregions 320 may be placed on all or portions of target 810 to facilitatetransfer of powder 430 to target 810 and/or to facilitate adhesion ofpowder 430 to target 810. In some embodiments of the invention, afterstep 243 the polarity of the charge on conductive region 320 is reversedto facilitate transfer of powder 430 to target 810 and/or to facilitateadhesion of powder 430 to target 810. As further detailed below, thepowder portions 430 may eventually be associated with LEEs in a lightingsystem to, e.g., wavelength convert at least a portion of the lightemitted by the LEEs.

In some embodiments target 810 is substantially optically transparent ortranslucent. In some other embodiments target 810 is substantiallyopaque. For example, target 810 may exhibit a transmittance orreflectance greater than 70% for optical wavelengths ranging betweenapproximately 400 nm and approximately 600 nm. Target 810 may include orconsist essentially of a material that is transparent to a wavelength oflight emitted by a LEE used in a lighting system (as described below)and/or phosphor 430. Target 810 may be substantially flexible or rigid.Target 810 may include or consist essentially of, for example, acrylic,polycarbonate, polyethylene naphthalate (PEN), polyethyleneterephthalate (PET), polycarbonate, polyethersulfone, polyester,polyimide, polyethylene, glass, paper or the like. In some embodiments,target 810 includes or consists essentially of multiple materials and/orlayers.

In some embodiments, the target 810 features one or more opticalelements formed therein or thereon. In some embodiments, one opticalelement is associated with each LEE, while in other embodiments multipleLEEs are associated with one optical element, or multiple opticalelements are associated with a single LEE, or no engineered opticalelement is associated with any LEE, for example a flat or roughenedsurface. In one embodiment target 810 includes elements or features toscatter, diffuse and/or spread out light generated by the LEE and/orphosphor 430. The optical elements may be formed by etching, polishing,grinding, machining, molding, embossing, extruding, casting, or thelike. The method of formation of the optical elements is not alimitation of embodiments of the present invention.

In some embodiments target 810 includes multiple layers, e.g., adeformable layer over a rigid layer, for example, a semicrystalline oramorphous material, e.g., PEN, PET, polycarbonate, polyethersulfone,polyester, polyimide, polyethylene, polyurethane, and/or paper formedover a rigid substrate, for example one including acrylic, aluminum,steel, or the like. Target 810 may have an electrical resistivitygreater than approximately 100 ohm-cm, greater than approximately 1×10⁶ohm-cm, or even greater than approximately 1×10¹⁰ ohm-cm.

In preferred embodiments of the present invention, the process describedabove transfers a uniform, well-controlled layer of phosphor powder froma template (system 300) to a target (target substrate 810). Phosphorpowder 430 may include or consist essentially of one or more separatedistinct powders. In one embodiment, multiple powders 430 are applied inone cycle of the process. In other embodiments a plurality of cycles ofthe process are performed to, for example, form a thicker layer ofpowder on target 810 or apply two or more different powders in sequence.

In some embodiments powder 430 is “fixed” on target 810 by theapplication of an adhesive, epoxy or other similar material afterapplication of powder 430. For example, in one embodiment a transparentepoxy 910 is applied over powder 430 as shown in FIG. 9. FIG. 9 depictsa structure 900 incorporating the powder regions 430 and a material 910thereover. Material 910 may include or consist essentially of atransparent material, e.g., a matrix material, encapsulant, or binder.In one embodiment, transparent material 910 includes or consistsessentially of silicone, epoxy or other suitable materials. Examples oftransparent material 910 include materials from the ASP series ofsilicone phenyls manufactured by Shin Etsu, or the Sylgard seriesmanufactured by Dow Corning. In FIG. 9 transparent material 910 is shownas having a substantially hemispherical shape, but this is not alimitation of the present invention and in other embodiments transparentmaterial 910 has a rectangular, square, or any other shape.

FIG. 10 depicts another embodiment of the invention in which atransparent material 910 is formed over target 810 before transfer ofpowder 430 from conductive regions 320, thereby forming a structure1000. In FIG. 10, transparent material 910 is shown as having twodifferent shapes, the leftmost two having a substantially rectangularshape and the rightmost having a substantially hemispherical shape. Inthese examples powder 430 is shown, as covering only the top oftransparent material 910 (leftmost material 910) and coveringsubstantially all of the exposed surfaces of transparent material 910(center and rightmost material 910). The shape of transparent material910 and the amount of coverage of powder 430 over transparent material910 is not a limitation of the present invention and these may havedifferent shapes and/or different coverage.

In some embodiments in which transparent material 910 is applied totarget 810 prior to transfer of powder 430, the optional step 246 (i.e.,removal of activation) is not necessary. In some embodiments in whichtransparent material 910 is applied to target 810 prior to transfer ofpowder 430, transparent material 910 is partially or substantially fullycured prior to the transfer of powder 430. In some embodiments in whichtransparent material 910 is applied to target 810 prior to transfer ofpowder 430, it may be advantageous for insulating substrate 310 tocomprise a “non-stick” material such as Teflon, or to include anon-stick coating over the surface or portion of the surface that maycome in contact with transparent material 910 so that transparentmaterial 910 does not stick to insulating substrate 310 or conductiveregions 320 during the transfer and separation process.

Any of the structures 800, 900, or 1000 may then be incorporated into alighting system 1100 that includes one or more LEEs, as exemplarilyshown in FIG. 11. The lighting system 1100, as shown, includes a LEEsubstrate 1110 and LEEs 1120 formed thereover. Target 810 is appliedover substrate 1110 such that powder portions 430 in transparentmaterial 910 are substantially aligned with LEEs 1120. In someembodiments a transparent material, for example a material identical orsimilar to transparent material 910, is placed between substrate 1110and target 810 to enhance optical coupling. In some embodiments such atransparent material is placed between substrate 1110 and target 810covering all or a portion of LEEs 1120 to reducetotal-internal-reflection (TIR) losses in LEEs 1120, to improve lightextraction, and/or to enhance optical coupling.

FIG. 12 shows a lighting system 1200 in accordance with variousembodiments of the invention. In one embodiment, the lighting system1200 incorporates structure 900 of FIG. 9. Structure 900 is applied tothe substrate 1110 such that transparent material 910 is substantiallyaligned with LEEs 1120 and covers all or some LEEs 1120, as shown inFIG. 12. In some embodiments an additional transparent material 910 or asimilar material may be applied to LEEs 1120 before mating with target810. As shown in FIG. 12, powder 430 is spaced apart from LEEs 1120,thus providing a remote-phosphor configuration in which the phosphor(powder 430) is not in direct contact with the LEE 1120. Thisconfiguration may provide the advantage of the phosphor remaining coolerthan if it were in direct contact with LEE 1120, and may reduceheat-induced efficiency degradation as well as provide longer lifetime.In other embodiments powder 430 is in contact or substantially incontact with LEE 1120.

FIG. 13 depicts a lighting system 1300 in accordance with anotherembodiment of the invention. In this embodiment, the target 810 alsoforms an optic that provides a desired light-distribution pattern whenincorporated into lighting system 1300. Target 810 includes or consistsessentially of optical elements 1310, which in FIG. 13 are eachsubstantially aligned with an LEE 1120. Target 810 typically features anarray of optical elements 1310; in some embodiments, one optical element1310 is associated with each LEE 1120, while in other embodimentsmultiple LEEs 1120 are associated with one optical element 1310, ormultiple optical elements 1310 are associated with a single LEE 1120, orno engineered optical element is associated with any LEE 1120, forexample portions of target 810 thereover may merely be flat or roughenedsurfaces. In one embodiment the optical elements 1310 scatter, diffuseand/or spread out light generated by LEE 1120.

Target 810 may be substantially optically transparent or translucent.For example, target 810 may exhibit a transmittance or reflectancegreater than 70% for optical wavelengths ranging between approximately400 nm and approximately 600 nm. Target substrate 810 may include orconsist essentially of a material that is transparent to a wavelength oflight emitted by LEE 1120 and/or powder/phosphor 430. Target 810 may besubstantially flexible or rigid. In some embodiments, target 810includes multiple materials and/or layers. Optical elements 1310 may beformed in or on target 810. For example, optical elements 1310 may beformed by etching, polishing, grinding, machining, molding, embossing,extruding, casting, or the like. The method of formation of opticalelements 1310 is not a limitation of embodiments of the presentinvention.

Optical elements 1310 associated with target 810 may all be the same ormay be different from each other. Optical elements 1310 may include orconsist essentially of, e.g., a refractive optic, a diffractive optic, aTIR optic, a Fresnel optic, or the like, or combinations of differenttypes of optical elements. Optical elements 1310 may be shaped orengineered to achieve a specific light-distribution pattern from thearray of light emitters, phosphors and optical elements.

As in system 1200, in system 1300 transparent material 910 may reduceTIR losses in LEEs 1120 and may provide enhanced optical couplingbetween LEEs 1120 and powder/phosphor 430. FIG. 13 also shows anoptional sealer 1320. Sealer 1320 seals the periphery of system 1300from external influences, for example humidity, corrosive ambients, etc.Sealer 1320 may include or consist essentially of, for example,adhesive, glue, tape, or the material of target 810 and/or substrate1110.

It should be noted that alignment, as used herein, may mean that thecenter of one structure, for example an LEE 1120, is aligned with thecenter of another structure, for example an optical element 1310;however, this is not a limitation of the present invention and in otherembodiments alignment refers to a specified relationship between thegeometries of multiple structures, as detailed above.

The illustrated embodiments of the invention feature a substantiallyflat target 810; however, this is not a limitation of the presentinvention. The method by which powder 430 is attached or attracted toconductive regions 320 is not dependent on conductive regions 320 and/orinsulating substrate 310 being flat and/or smooth, and in otherembodiments conductive regions 320 and/or insulating substrate 310 havearbitrary shapes. FIG. 14 depicts a system 1400 in accordance with oneembodiment of the invention in which target 810 has one or more curvedportions 1410. Such a target 810 may provide complete or substantiallycomplete coverage of powder 430 over LEEs 1120 in a remote-phosphorconfiguration, and may also reduce or eliminate any gap between target810 and substrate 1110. FIG. 15 shows an embodiment of insulatingsubstrate 310 and conductive regions 320 that may be used to make thestructure shown in FIG. 14. As described above, powder 430 is picked upon conductive regions 320, as shown in FIG. 15. Powder 430 is thentransferred to target 810. Target 810 with powder 430 is then mated to asubstrate 1110 having LEEs 1120 and transparent material 910, as shownin FIG. 16. In this case transparent material 910 is shown as beingformed over all or a portion of each LEE 1120 prior to mating withtarget 810 and powder 430. In one embodiment powder 430 is transferredto transparent material 910, instead of target 810, before mating oftarget 810 with substrate 1110. Substrate 1110 may be affixed to target810 by transparent material 910 or a similar material and/or by othermeans, for example adhesive, glue, tape, or the like. In one embodiment,double-sided tape, such as 3M 467MP, is used to affix substrate 1110 totarget 810. In one embodiment a liquid adhesive, such as Dymax 3099, isused to affix substrate 1110 to target 810.

In some embodiments of the invention, target 810 includes one or moreLEEs prior to powder/phosphor 430 being incorporated therewith. FIG. 17depicts a system 1700 in accordance with various embodiments of theinvention. As shown, system 1700 includes substrate 1110 having one ormore LEEs 1120 formed thereover. A transparent material 910 and a powder430 are formed over the LEEs 1120. FIG. 18 shows the structure of FIG.17 at an early stage of manufacture. FIG. 18 shows an insulatingsubstrate 310 having conductive regions 320, one or more of which has aconcave shape. (As utilized herein, a “concave” shape is one thatextends inward, thus forming a cavity or depression, but is notnecessarily smooth or rounded, e.g., corresponding to a portion of asphere or ellipse, and may also be designated an “indented” shape. And,a shape “complementary” to an indented shape has a shape “mirroring” theindented shape such that the two shapes fit together. For example, acomplementary shape to a concave shape may be convex.) Powder 430 isattached to the concave-shaped conductive regions 320 and then matedwith the transparent material 910 over the LEEs 1120 on substrate 1110,which preferably have a complementary shape. After mating of substrates310, 1110, transfer of powder 430, and removal of insulating substrate310 and conductive regions 320, the structure of FIG. 17 is produced.Transparent material 910 may then be fully or partially cured. Inanother embodiment, the transparent material 910 is formed into theconcave regions of conductive material 320 over powder 430 prior tomating with substrate 1110.

The same powder-deposition technique may be used to produce phosphorunits that may then be subsequently applied to LEEs, for example using apick-and-place tool. FIG. 19 shows one embodiment of such an approach,in which a transparent material 910 is formed over a surface 1910. Thetransparent material 910 may be cast into a mold or spread on thesurface or formed by other techniques. Powder 430 (attached toconductive regions 320) is mated with transparent material 910, andpowder 430 is transferred to transparent material 910 as shown in FIG.20. Transparent material 910 may be partially cured prior to powdertransfer. After transfer of powder 430, the transparent material 910 maybe cured. In one embodiment, transparent material 910 with powder 430,as shown in FIG. 20, may be mated with multiple LEEs, where each powderportion 430 is substantially aligned with a LEE. In one embodiment,transparent material 910 is divided into sections, each of whichincluding one or more powder portions 430, and each section may be matedwith one or more LEEs.

In one embodiment, the surface 1910 includes one or more protrusionsand/or one or more indentations which are then replicated (in negative,complementary form) in the transparent material 910. FIG. 21 shows oneembodiment in which surface 1910 has multiple protrusions 2110 that forma void region or well 2120 in transparent material 910 that fits overone or more LEEs upon alignment with the LEE(s).

Another exemplary embodiment is shown in FIG. 25. The formation of thestructure of FIG. 25 starts with insulating substrate 310 and conductiveregions 320 as shown in FIG. 22, where the conductive regions 320 areformed in and conform to the sidewalls of wells (i.e., a type of concavestructure that may have substantially straight sidewalls) in substrate310. As shown, powder 430 is then attached to conductive regions 320.Next, transparent material 910 is formed into the wells of powder 430,as shown in FIG. 23 (insulating substrate 310 shown turned over in FIG.23, but this is not a limitation of the present invention). In the nextstep, as shown in FIG. 24, a mold 2410 is mated with insulatingsubstrate 310, where the mold 2410 has one or more protrusions thatsubstantially align with the wells of conductive material 320.Transparent material 910 is then cured and removed from mold 2410 andthe wells in conductive material 320, leaving the structure shown inFIG. 25. In one embodiment each indentation in the structure in FIG. 25is placed over one or more LEEs.

In general herein, powder 430 is shown as disposed on top of transparentmaterial 910; however, in other embodiments powder 430 is infusedcompletely or partially into transparent material 910. In one embodimentpowder 430 is formed as a layer at the edge of transparent material 910,but it may also be substantially or completely encased by transparentmaterial 910. The extent to which powder 430 sits on the surface or isabsorbed by or covered by transparent material 910 may be controlled bycontrolling the formation conditions and material properties, forexample particle size and density, viscosity, and processing temperatureof transparent material 910. In some embodiments, transparent material910 is hardened by curing, for example by thermal or light-based curing.In one embodiment, the extent to which powder 430 extends into and/or iscovered by transparent material 910 is controlled by the viscosity andprocessing temperature. Lower viscosity will generally result inincreased extension into and/or coverage, while higher viscosity willgenerally result in decreased extension into and/or coverage. Extensioninto and coverage of powder 430 by transparent material 910 may also becontrolled by performing a partial or complete cure at some time afterpowder transfer, that time being determined by the desired extent ofextension into and/or coverage of powder 430 by transparent material910. In one embodiment the powder 430 composition may be graded toachieve a desired powder 430 composition profile within transparentmaterial 910. For example, in one embodiment the powder 430 compositionmay be graded to monotonically increase in the direction away from LEE1120. However this is not a limitation of the present invention and inother embodiments the powder 430 composition may be monotonically gradedin the opposite direction, or may be graded in a non-monotonic profile,or may have any arbitrary profile. In some embodiments powder 430 mayinclude or consist essentially of multiple different powders each havinga different profile.

In one embodiment, the pattern of conductive regions 320 (for example asshown in FIG. 7) represents the desired distribution of phosphor powder.In one embodiment, the pattern of conductive regions 320 representsconductive addressable “pixels” that may be selectively activated andde-activated, to permit production of different patterns of powder 430using the same system.

The embodiments discussed above show the insulating substrate 310 (e.g.,in FIG. 3) as being substantially flat; however, this is not alimitation of the present invention and in other embodiments insulatingsubstrate 310 is curved or has any arbitrary shape. In some embodiments,the conductive substrate 310 is formed into a cylinder or drum to permitcontinuous or roll-to-roll processing, for example in a mode that issimilar to a printing press, photocopier, or laser printer.

In various embodiments discussed above, the phosphor powder is attractedor attached to regions that have been activated. In other embodiments,the phosphor powder is attracted to substrate 300, and regions 320 areactivated to form regions not attractive to the phosphor powder.

In one embodiment, the processes shown in FIGS. 1 and 2 are performedusing a photoconductive surface instead of the conductive regions 320shown in FIG. 3. The photoconductive surface is light-sensitive (and mayalso be called a photoreceptor) and typically includes or consistsessentially of a thin layer of photoconductive material. In someembodiments, the photoconductive material is applied to a flexible beltor drum.

The photoconductive surface may be selectively charged by exposure tolight, and the selectively charged regions may attract the powder forsubsequent deposition, as shown in FIG. 26. Per step 210 of FIG. 1, aphotoconductive surface 2620 is provided. In one embodiment, thephotoconductive surface 2620 is unsupported (i.e., free-standing), whilein another embodiment photoconductive surface 2620 is formed on asupport structure 2630, as shown in FIG. 26.

Activation of the photoconductive surface 2620 occurs next, per step 220of FIG. 2. In one embodiment, activation is a two-part process, as shownin FIGS. 27A and 27B. The photoconductive surface 2620 is typicallyinsulating when not illuminated but becomes conducting upon exposure tolight. Surface 2620 is first charged without illumination, for example,by applying a high DC voltage to wires adjacent to photoconductivesurface 2620. The voltage produces an electric field near the wires thatcauses the air molecules to ionize. Ions of the same polarity as thevoltage on the wires deposit on photoconductive surface 2620, creatingan electric field across surface 2620 and resulting in a uniform orsubstantially uniform charge 2710 over photoconductive surface 2620, asshown in FIG. 27A. While FIG. 27A shows photoconductive surface 2620having a positive charge, in other embodiments photoconductive surface2620 has a negative charge.

Next, one or more portions of the photoconductive surface 2620 areexposed to light 2720 that discharges the illuminated regions thereof,causing a localized reduction in the electric field, as shown in FIG.27B. The unilluminated (or dark) areas retain their charge 2710′. Byselectively illuminating charged photoconductive surface 2620, a chargeimage may be formed thereon. The image represented by the chargedportions will attract the powder in subsequent steps. In one embodiment,photoconductive surface 2620 is exposed or illuminated by one or morescanning modulated lasers or an LED image bar. In one embodimentillumination occurs from light reflected from an illuminated image.

In step 230 (FIG. 2), powder 430 is attached to the activated portionsof photoconductive surface 2620, as shown in FIG. 28. In one embodimentpowder 430 is charged with a polarity opposite that on photoconductivesurface 2620. In one embodiment, powder 430 is charged via thephenomenon of triboelectricity (i.e., static electricity). In someembodiments, powder 430 is mixed with and optionally charged bymagnetized carrier beads that may be used to transport powder 430 todifferent zones in a manufacturing tool. The electric field associatedwith the charge pattern of the image on photoconductive surface 2620exerts an electrostatic force on charged powder 430, which then adheresto the charge pattern on photoconductive surface 2620. The powder may besupplied to the structure shown in FIG. 28 in a variety of ways; oneembodiment is shown in FIG. 4B. In other embodiments, powder 430 ispoured over photoconductive surface 2620. In some embodiments, powder430 is applied by rolling a photoconductive surface 2620 in the form ofa drum or reel through or over powder 430.

In step 250 (FIG. 2), powder 430 is transferred from photoconductivesurface 2620 to target 810, as shown in FIG. 29. In one embodiment, thetransfer is performed by bringing target 810 into contact with powder430 and then applying a charge with a polarity opposite to that ofpowder 430. The charge is generally strong enough to overcome the powderadhesion to photoconductive surface 2620. Target 810 is then releasedwith a second controlled charge. At this point in the process, powder430 has been transferred from photoconductive surface 2620 to target810, as shown in FIG. 29.

In one embodiment, the process described in conjunction with FIGS. 26-29is performed with dry powder. In one embodiment, the process describedin conjunction with FIGS. 26-29 is performed using equipment similar toa photocopier or a laser printer. In one embodiment, the processesdescribed with respect to powder transfer may include a further step ofcleaning the powder off of support 2630 and/or photoconductive surface2620. In one embodiment, such cleaning is performed using a rotatingbrush. The cleaning may even be performed by blowing the powder off ofthe drum.

In some embodiments, powder 430 includes or consists essentially of alight-conversion material, for example a phosphor (with or without anaccompanying polymer). In some embodiments, powder 430 comprises one ormore phosphor powders and one or more polymer powders or particles. Inone embodiment, after transfer of powder 430 to target 810, powder 430is heated to melt or partially melt the polymer, which acts to fix thephosphor powder in place. In some embodiments, the polymer issubstantially transparent to a wavelength of light emitted by LEEs 1120and/or powder 430.

FIG. 30 shows one embodiment of the present invention incorporating aroll-to-roll process. System 3000 includes or consists essentially oftarget 810, a supply roll 3010 for target 810, substrate 1110, a supplyroll 3015 for substrate 1110, LEEs 1120 formed over substrate 1110 usinga die-attach tool 3035, a dispenser 3070 to dispense binder 910 overpowder 430, a photoconductive surface 3025 over drum 3020, anilluminator 3050, and a scanning system 3060 to permit scanning of light3051 from illuminator 3050 onto photoconductive surface 3025. Light 3051from illuminator 3050 is scanned onto photoconductive surface 3025 togenerate an electrostatic image on photoconductive surface 3025, whichattracts powder 430, leaving powder 430 selectively attached tophotoconductive surface 3025. The selectively attached powder 430 onphotoconductive surface 3025 is then transferred to target 810. Binder910 is dispensed over powder 430 prior to mating with substrate 1110 andLEEs 1120, forming the lightsheet identified as 1200 in FIG. 12. Thelightsheet 1200 is then taken up on a final roll 3090. Powder 430 isstored in a container 3030 and attached to photoconductive surface 3025through a roller 3040. Illuminator 3050 may include or consistessentially of one or more lasers or one or more LEDs. In someembodiments, binder 910 is formed over LEEs 1120 before mating withpowder 430 and target 810. In some embodiments, LEEs 1120 are attachedto substrate 1110 prior to this process—in this case supply roll 3015dispenses substrate 1110 over which LEE 1120 have been formed.

FIG. 31 shows another embodiment of the present invention incorporatinga roll-to-roll process. System 3100 includes or consists essentially ofsubstrate 1110 and supply roll 3015 for substrate 1110, LEEs 1120 formedover substrate 1110 using die-attach tool 3035, dispenser 3070 todispense binder 910 over LEEs 1120, photoconductive surface 3025 overdrum 3020, illuminator 3050, and scanning system 3060 to permit scanningof light 3051 from illuminator 3050 onto photoconductive surface 3025.Light 3051 from illuminator 3050 scanned onto photoconductive surface3025 generates an electrostatic image on photoconductive surface 3025,which attracts powder 430, leaving powder 430 selectively attached tophotoconductive surface 3025. Powder 430 is then transferred fromphotoconductive surface 3025 to binder 910, forming the lightsheet shownin FIG. 17. The lightsheet is then taken up on final roll 3090.

FIGS. 30 and 31 show two embodiments; other embodiments have additionalor fewer steps or components or may be carried out in a different order.All or some of the components shown in FIGS. 30 and 31 may be similar tothose used in laser printers, LED printers, photocopiers, or the like.In some embodiments, powder 430 is transferred to target 810 using oneor more conductive regions 320 formed on an insulating substrate 310 inthe form of a drum or reel. Binder 910 may be cured during the processesillustrated in FIGS. 30 and 31, and/or conductive traces may be formedon substrate 1110 prior to formation or placement of LEEs 1120 oversubstrate 1110.

In general, in the above discussion the arrays of light emitters, wells,optics and the like have been shown as square or rectangular arrays;however, this is not a limitation of the present invention and in otherembodiments these elements are formed in other types of arrays, forexample hexagonal, triangular, or any arbitrary array. In someembodiments these elements are grouped into different types of arrays ona single substrate.

The terms and expressions employed herein are used as terms andexpressions of description and not of limitation, and there is nointention, in the use of such terms and expressions, of excluding anyequivalents of the features shown and described or portions thereof. Inaddition, having described certain embodiments of the invention, it willbe apparent to those of ordinary skill in the art that other embodimentsincorporating the concepts disclosed herein may be used withoutdeparting from the spirit and scope of the invention. Accordingly, thedescribed embodiments are to be considered in all respects as onlyillustrative and not restrictive.

What is claimed is: 1.-16. (canceled)
 17. A roll-to-roll apparatus forfabricating phosphor arrangements, the apparatus comprising: a firstroll for supplying a continuous length of a flexible substrate material;a second roll for accepting the continuous length of flexible substratematerial from the first roll; a die-attach tool for attachinglight-emitting elements to the flexible substrate material as theflexible substrate material travels from the first roll to the secondroll; a rotatable drum having a photoconductive surface and configuredto dispose portions of phosphor over the flexible substrate material asthe flexible substrate material travels from the first roll to thesecond roll; disposed over at least a portion of the drum, a firstdispenser for dispensing phosphor powder over the photoconductivesurface; and an illuminator for selectively illuminating portions of thephotoconductive surface as the drum rotates to generate an electrostaticimage on the photoconductive surface, regions of the electrostatic imagebeing attractive to the dispensed phosphor powder, wherein the secondroll accepts flexible substrate material having light-emitting elementseach with a phosphor portion disposed thereover.
 18. The apparatus ofclaim 17, further comprising, disposed between the die-attach tool andthe drum, a second dispenser for dispensing a binder material over thelight-emitting elements after attachment thereof to the flexiblesubstrate material.
 19. The apparatus of claim 17, further comprising ascanning system for scanning light from the illuminator over thephotoconductive surface.
 20. A roll-to-roll apparatus for fabricatingphosphor arrangements, the apparatus comprising: a first roll forsupplying a continuous length of a flexible substrate material; a secondroll for accepting the continuous length of flexible substrate materialfrom the first roll; a third roll for supplying a continuous length of asecond substrate material; a die-attach tool for attachinglight-emitting elements to the second substrate material after thesecond substrate material is supplied by the third roll; a rotatabledrum having a photoconductive surface and configured to dispose portionsof phosphor over the flexible substrate material as the flexiblesubstrate material travels from the first roll to the second roll;disposed over at least a portion of the drum, a first dispenser fordispensing phosphor powder over the photoconductive surface; anilluminator for selectively illuminating portions of the photoconductivesurface as the drum rotates to generate an electrostatic image on thephotoconductive surface, regions of the electrostatic image beingattractive to the dispensed phosphor powder; and an arrangement ofrollers configured to bring the second substrate material and theflexible substrate material in proximity at a joining location after (i)light-emitting elements have been attached to the second substratematerial and (ii) phosphor portions have been disposed over the flexiblesubstrate material, thereby enabling transfer of the light-emittingelements to the phosphor portions over the flexible substrate material,wherein the second roll accepts flexible substrate material havinglight-emitting elements each with a phosphor portion disposed thereover.21. The apparatus of claim 20, further comprising, disposed between thedrum and the joining location, a second dispenser for dispensing abinder material over the phosphor portions after disposal thereof overthe flexible substrate material.
 22. The apparatus of claim 20, furthercomprising a scanning system for scanning light from the illuminatorover the photoconductive surface.
 23. The apparatus of claim 17, whereinthe regions of the electrostatic image attractive to the dispensedphosphor powder correspond to portions of the photoconductive surfaceilluminated by the illuminator.
 24. The apparatus of claim 17, whereinthe regions of the electrostatic image attractive to the dispensedphosphor powder correspond to portions of the photoconductive surfacenot illuminated by the illuminator.
 25. The apparatus of claim 17,wherein the first dispenser comprises (i) a container for phosphorpowder, and (ii) a roller disposed between the container and the drum.26. The apparatus of claim 17, wherein the illuminator comprises one ormore lasers.
 27. The apparatus of claim 17, wherein the illuminatorcomprises one or more light-emitting diodes.
 28. The apparatus of claim17, further comprising, disposed between the drum and the second roll, aheater for heating dispensed phosphor powder.
 29. The apparatus of claim17, further comprising a cleaning mechanism for cleaning phosphor powderoff of the drum.
 30. The apparatus of claim 29, wherein the cleaningmechanism comprises at least one of a brush or a blower.
 31. Theapparatus of claim 17, further comprising phosphor powder disposedwithin the first dispenser.
 32. The apparatus of claim 31, wherein thephosphor powder is charged.
 33. The apparatus of claim 31, wherein thephosphor powder is mixed with magnetized carrier beads.
 34. Theapparatus of claim 18, further comprising, disposed between the seconddispenser and the second roll, a heater for heating dispensed bindermaterial.
 35. The apparatus of claim 20, wherein the regions of theelectrostatic image attractive to the dispensed phosphor powdercorrespond to portions of the photoconductive surface illuminated by theilluminator.
 36. The apparatus of claim 20, wherein the regions of theelectrostatic image attractive to the dispensed phosphor powdercorrespond to portions of the photoconductive surface not illuminated bythe illuminator.
 37. The apparatus of claim 20, wherein the firstdispenser comprises (i) a container for phosphor powder, and (ii) aroller disposed between the container and the drum.
 38. The apparatus ofclaim 20, wherein the illuminator comprises one or more lasers.
 39. Theapparatus of claim 20, wherein the illuminator comprises one or morelight-emitting diodes.
 40. The apparatus of claim 20, furthercomprising, disposed between the drum and the second roll, a heater forheating dispensed phosphor powder.
 41. The apparatus of claim 20,further comprising a cleaning mechanism for cleaning phosphor powder offof the drum.
 42. The apparatus of claim 41, wherein the cleaningmechanism comprises at least one of a brush or a blower.
 43. Theapparatus of claim 20, further comprising phosphor powder disposedwithin the first dispenser.
 44. The apparatus of claim 43, wherein thephosphor powder is charged.
 45. The apparatus of claim 43, wherein thephosphor powder is mixed with magnetized carrier beads.
 46. Theapparatus of claim 21, further comprising, disposed between the seconddispenser and the second roll, a heater for heating dispensed bindermaterial.